Re: [PATCH 0/3] PM / ACPI / i2c: Runtime PM aware system sleep handling

[Ulf Hansson <ulf.hansson@linaro.org>]

On 29 August 2017 at 16:43, Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
> On Tuesday, August 29, 2017 1:44:11 PM CEST Ulf Hansson wrote:
>> On 29 August 2017 at 12:29, Johannes Stezenbach <js@sig21.net> wrote:
>> > Hi,
>> >
>> > On Tue, Aug 29, 2017 at 02:18:13AM +0200, Rafael J. Wysocki wrote:
>> >> On Wednesday, August 23, 2017 4:42:00 PM CEST Ulf Hansson wrote:
>> >> > The i2c designware platform driver, drivers/i2c/busses/i2c-designware-platdrv.c,
>> >> > isn't well optimized for system sleep.
>> >> >
>> >> > What makes this driver particularly interesting is because it's a cross-SoC
>> >> > driver, which sometimes means there is an ACPI PM domain attached to the i2c
>> >> > device and sometimes not. The driver is being used on both x86 and ARM.
>> > ...
>> >> Basically, the point is to allow i2c-designware-platdrv to point its late
>> >> suspend and early resume callbacks, respectively, to pm_runtime_force_suspend()
>> >> and pm_runtime_force_resume() which then will do the right thing regardless of
>> >> whether or not the device is runtime suspended when system suspend starts.
>> >
>> > I'd like to point out a comment added by Hans de Goede in
>> > https://bugzilla.kernel.org/show_bug.cgi?id=193891#c99
>> >
>> >   The D0 / D3 methods of some devices use ACPI OpRegions on the PMIC which is
>> >   attached to I2C7, these methods get executed by acpi_dev_suspend_late /
>> >   acpi_dev_resume_early. Since the i2c-designware driver uses regular suspend /
>> >   resume callbacks it is already suspended at the time those calls happen,
>> >   leading to a device-suspend error and the system not suspending at all.
>>
>> Yes, that's why I moved those operation to be managed at the
>> ->suspend_late() in my series, and at the same time prevent the
>> direct_complete patch from executed for this device.
>>
>> >
>> > It's the reason for the Cherrytrail I2C7 special treatment in
>> > i2c-designware-platdrv.c and pm_disabled = true in i2c-designware-baytrail.c,
>> > however pm_disabled seems to be a problem for S0ix support.
>> > To solve it, i2c-designware-platdrv needs to suspend after all
>> > devices using ACPI OpRegions for suspend.
>> >
>> >
>> > Johannes
>>
>> Did you try out my series (v2) if that could fix this problem in a
>> more flexible manner?
>>
>> In other words, is it fine if the device remains runtime PM enabled
>> during the entire device_suspend() phase, and also not being suspended
>> until ->suspend_late()?
>
> Ulf, please, this is a *different* problem.

Yes, it is!

Just wanted to point out that if the device remains runtime PM enabled
the entire device_suspend() phase, that *could* solve the problem.

>
> Can we focus on one problem at a time?

Yes!

However, there is lots of things following when we try to enable the
runtime PM centric path for ACPI. :-)

Kind regards
Uffe